| Birth Date: | 8 February 1936 |
| Birth Place: | Stockholm, Sweden |
| Death Date: | 18 January 2003 (aged 66) |
| Death Place: | Stockholm, Sweden |
| Height: | 182 cm |
| Weight: | 78 kg |
| Sport: | Sailboat racing |
| Club: | Royal Swedish Yacht Club |
| Show-Medals: | yes |
Lars Stefan Sundelin (8 February 1936 – 18 January 2003) was a Swedish sailor. He was a cousin of the brothers Jörgen, Peter and Ulf Sundelin who competed as a team at the 1968 and 1972 Olympics and at the world championships in between. At the 1976 Summer Olympics Ulf was replaced by Stefan, and the Sundelin team finished ninth in the three-person keelboat event.